Expansible piston



Jan. 29 1946. J. D. BUCHANAN 2,393,747

EXPANSIBLE' PI'sTjpN Filed April 21 1945 JD,BUCHANAM INVENTOR.

ATTORNEY f Patented Jan. 29, 1946 UNITED STATES P'AjTENT OFFICE EXPANSIBLE PISTON D. Buchanan, Burbank; Gold. Application April 21, 1945, Serial No. 589,570

'7 Claims.

The invention relates. to an expansible piston adapted for various uses such as. the p ston of a work cylinder to. which fluid pressure is applied on opposite sides. of the pis on. in order to recipocate the. piston and its connected mechanism. h piston of this invention may a so be employed as a relief or blow-oil valve.

An object. o the vent on is to av id the e essity of machining the piston to fit its cylinder with, a. close tolerance, while making it possible. to manu ly adjust th workin fit of the piston with the cylind r. The invention also provides means whereby the fluid ressurev is operative to pand t e piston and effect a sealin contact with the. cylinder.

For further details of the invention, eferenc may be made t the drawing, wherein:

ure 1 is a ngitudinal section l v ew of a work cylinder provided with one form of expansible piston according to the present invention Fig. 2 is a longitudi al sectional v ew of. a r i valve hav n a m dified form of p ston. accordin to the present invention. 7

Fig. 3 is a sectional, view on. line 33 of Fla. 2..

Referrin in detail to the drawing, in Fig. 1 the work cylinder is provided with an expansible piston 2 having a suitable piston od 3.. Fl id pressure and exhaust lines 4 and 5 are connected to the opposite ends of the cylinder 1, so. that the piston 2 may be reciprocated as is well known, to thereby reciprocate whatever mechanism is connected to the piston rod 3.

The piston 2 comprises in part a hub 6 suitably secured on the piston rod 3. For example, the hub 6 may have a tapered bore which fits on a correspondingly tapered portion 8 on the end of the piston rod 3. The hub 6, at one side thereof, has a flange extension 9 which serves as an abutment. Hub 6 also has a cylindrical surface ID on which are slidably mounted two cam rings l l and I2. The inner periphery of each cam ring II and I2 is provided with ring seals l3 and I4, respectively, to prevent leakage between the hub 6 and the inner periphery of these cam rings. The cam rings I I and 12 at their outer peripheries have conical cam surfaces [5 and I6, respectively, which support an expansible piston ring I! having corresponding cam surfaces I8 and. l 9 on its inne periphery.

The piston ring I! may be an endless one-piece ring of metal such as tempered steel and it is machined to fit the bore of the cylinder I with a tolerance such that when ring I! is not expanded it fits the bore of the cylinder too loosely, the tolerance being such that the ring I! can be expanded without exceeding the elastic limit of the ring, to fit the cylinderbore.

19, respectively, on the piston ring I! are preferably ground and lapped to accurately fit each other and provide a fluid seal to prevent leakage between the Piston ring I! and the cam rings H a d 1 The piston ring H- may be expanded to fit the cylinder bore by reducing the separation of the cam rings II and I2 and for this purpose the outer end of connecting rod 3 is provided with disk 20 which may be compressed by a nut 2| having a suitable lock nut 22,.

Inthis way, the piston ring I] may be machilled to. fit the cylinder bore with a large tolerance, and the disk 2!! may be advanced to compress the cam rings H and ['2 between disk 20 and the abutment 9, until the desired close fit is obtained between the outer periphery of the piston ring l'l and the cylinder bore.

In order to provide for further and automatic expansion of the piston ring I] by fluid pressure, viz, in the event of leakage past that ring, preferably the area of each of the outer faces of rings II and I2, that is, the faces exposed to fluid; pressure in the cylinder, is greater than th p riphe l a e o piston ring. l1 wher by e if ence i press on su h areas is. ope ativ to slide eith r cam r n I l or cam r ng 2, depending on which one is subjected to pressure, to further expand the piston ring l1 and reduce or stop the leakage.

The expansible piston of Fig. 1 may also be used in the blow-01f valve 23 of Fig, 2, or in other types of cylinders, and, likewise, the expansible piston 24 in Fig. 2 may be used in the work cylinder I of Fig. 1 or with other types of cylinders.

In Fig. 2, the fluid pressure in the inlet 25 is relieved in a suitable outlet 26, when the pressure on the pressure side of piston 24 sufliciently overcomes the spring 21 or the like to advance the piston 24 beyond the outlet 26, as well known. The expansible piston 24 is similar to that above described, except that the seals I3 and. I4, instead of being ring seals arranged in the cam rings II and I2, comprise a hub ring 28 like piston ring l1, except that it is compressible to fit the cylindrical surface 29 of the hub 30. Also, the outer periphery of the hub ring 28 is provided with inverted V-shaped conical fluid seal cam surfaces 3| and 32 which fit corresponding conical surfaces 33 and 34, respectively, on the inner periphery of the cam rings 35 and 36. As previously described in connection with Fig. 1, the cam rings 35 and 36 at their outer peripheries also have conical cam surfaces 31 and 38 which fit the cam 7 to make the inner periphery of the hub ring 28 fit the periphery 29 of the hub .30, to prevent leakage. The movable abutment-or disk 43 is held in position by suitable means, as above described, namely, by a nut 45-having a suitable lock nut 46.

It will be apparent also that the inner periphcry of the hub ring 28 need be machined to fit the hub 30 only within limits determined by the amount with which the hub ring 28 may be compressed without exceeding its elastic limit.

If leakage occurs between either the outer periphery of piston ring 4| and the wall of the cylinder 44, or between the inner periphery of hub ring 28 and the hub 39, such leakage is automatically reduced or stopped, as the outer faces of the cam rings 35 and 35 each preferably have an area which is greater than both the outer periphery of piston ring 4| and the inner periphery of hub ring 28, whereby the difference in such fluid pressure is operative to. further compress the cam rings 35 and 36 and, hence, further expand the piston ring4l and further compress the hub ring 28. T

, It will be apparent that various modifications may be made in the invention without departing from the spirit of the following claims. For example, use may be made of more than two cam rings such as rings II and H. in Fig. l, witha piston ring like ring I! for each two adjoining cam rings. Also, hub ring 28 may be made of various compressible materials such as rubber, rubber substitute material, or the like.

I claim: v I

l. A piston having a hub, spaced cam rings on said hub, an expansible piston ring having inner and outer peripheries, one of said peripheries being cylindrical, and the other periphery having oppositely inclined cam surfaces, said cam rings each having a cam surface fitting one of the cam surfaces on said'piston ring, all of said cam surfaces cooperating to expand said piston ring when the distance between said cam rings is reduced, and adjustable means on saidhub for adjusting the separation of said cam rings to adjustably expand said piston ring.

2. A piston comprising a hub, a cam suport surrounding and slidable on said hub, an abutment therefor, a seal between said cam support and said hub, a cam piston ring surrounding and fitting on said support, and adjustable means on said hub for operating said cam support to expand said piston ring, said cam support acting as a fluid pressure operated piston to also expand said piston ringQ V 3. A piston according to claim 2 wherein said cam piston ring is a one piece endless ring of tempered steel.

4. A piston according to claim 2 wherein said cam piston ring is provided at each side of its inner periphery with a conical face tapering inface fitting one of the cam. surfaces on said piston ring, all of said cam surfaces comprising fluid seals and cooperating to expand said piston ring when the distance between said cam rings is reduced, and adjustable means on said hub for adjusting the separation of said cam rings to adjustably expand said piston ring.

6. A piston according to claim 5 wherein said first-mentioned seal comprises a ring on said hub, and cooperating fluid seal cam surfaces on said hub ring and on said cam rings.

7. A piston having a hub,a compressible ring on said hub, an expansible piston ring, and means comprising a cam ring having two cam surfaces for expanding said piston ring and compressing said hub ring. I

J. D. BUCHANAN. V 

